Known work stations use a specific CPU, e.g. an Intel 80386 microprocessor, provided on a system board together with other chip units such as memories, various peripheral interfaces and a system bus controller. The CPU and the above mentioned devices communicate with each other, partially through buffers, over a local bus comprising control, address and data lines. In general, the system design is tailored for the specific CPU. This means, that a large variety of different chip units are required for work stations using different CPUs. The local bus also is tailored for the specific configuration. In order to maintain compatibility with other systems, detailed specifications rigidly determine the features and functions of the various units and their I/O registers. Thus, it is difficult to modify the system for expansion and improved performance.
Depending on the specific design of the system board and the units to be connected thereto, it is necessary to configure the units of the system board and the cards to be connected thereto, for example when installing the system or making any changes thereto. At one time this was done by switches and other mechanical devices. Recently such mechanical means have been replaced by a so-called Programmable Option Select (POS) installing program which serves to configure the system board and the adapters in a setup mode. With a predetermined rigid system board design, a very small predetermined number of units of the system board are activated via separate setup lines and configured accordingly.
However, if it is desired to have the system board considerably expanded by a varying number of further units, configuring thereof becomes difficult. The main reason for that is that the number of addresses assigned to I/O registers on the system board are rather limited and are occupied or reserved for various purposes.